JPH0547303B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application of the Invention The forming method of the present invention relates to a sheet metal forming method in which a processed product is placed between concave and convex surfaces of opposing dies at regular intervals. In particular, the method of the present invention is a method for forming a thin-walled, semi-annular shell from a flat thin sheet material, in which the flat thin sheet material is first formed into a cylindrical band, welded, and then curled inward to form a cylindrical shell on the die surface. A compression method that eliminates weld tensile failure and accurately aligns the workpiece to the die surface.

BACKGROUND OF THE INVENTION The method of the present invention is suitable for forming annular shells (doughnut-shaped hollow bodies) with thin walls, annular grooves, and a generally U-shaped (or laterally bisected) cross-section. These shells are currently used in liquid couplings or transmissions in which radially extending vanes (or fins) are fixed in grooves in the outer surface of the shell to form a rotor. Two rotors are used in automotive torque converters that form an annular hollow body with blades in open, facing relationship. Therefore, the outer surface shape of the semi-annular shell is important to the proper operation of the torque converter. for example,
Tolerances on the outside of semi-annular shells used in automotive torque converters must be maintained at ±5% of the material thickness. Therefore, the thickness is 0.1016cm
(0.040in) annular shell tolerance is ±0.051cm
(0.002in).

Annular shells are currently formed industrially by cutting or stamping washer-like blanks from flat sheet metal stock, resulting in significant material waste and increasing the cost of the shell. The blank is then formed into a semi-annular shell using conventional die stamping techniques.

Problems to be Solved by the Invention The method of the invention substantially eliminates scrap;
Therefore, reduce the cost of Ciel. U.S. Patent No. 3,851,517, assigned to General Motors Co.
A method for forming semicircular shells from flat strip stock that eliminates scrap has been disclosed, but has not been commercially successful. The method disclosed in this patent utilizes rectangular sheet metal stock, which is rolled into a cylinder and welded. The cylinder end is then forced into a first preform die set to first bend the top edge of the cylinder outward. The outwardly curved end (flare) of the cylinder is then forced into a second curling die set having regularly spaced die concave surfaces and matching outwardly curved die convex surfaces to place the cylinder under tension. Curl outwards to form a semicircular shell. Finally, the shell is formed into its final shape in a third restriking die set.

The weldment had to be precisely adjusted, flattened, and smoothed before forming because the weld was placed under extreme tensile stress during curl forming. Nevertheless, the method disclosed in the aforementioned U.S. Pat. No. 3,851,517 was not commercially successful because the weld repeatedly broke under the tensile stress caused by curling the cylinder outward. The method was eventually abandoned. Additionally, the workpiece tends to pull away from the die concavity under the tensile forces created by the curling process, making it difficult to control subcritical tolerances in the shell.

The method of the invention involves curling the cylindrical band inward and placing the weldment in compression.
Eliminate the problems inherent in said patent. In fact, the semi-annular shell can be made by welding (or joining) the abutting portions of the bands by other means by the method of the invention.
It can be molded without molding. And the method is also suitable for other applications. Furthermore, because the shell can be formed in one press stroke, there is no need for preforming of the cylindrical flare required in the aforementioned patent.

B. Structure of the Invention The method for forming a thin-walled, semi-annular shell of the present invention involves forming a rectangular flat sheet into a cylindrical band, and desirably, particularly for the semi-annular shell, the mating free ends of the cylindrical band are including joining.
One end of the cylindrical band is then forced into a die set having a cylindrical opening that blends smoothly into an inwardly curled semi-annular space defined by opposing regularly spaced concave and convex die surfaces.
The diameter of the cylindrical band is equal to the nominal diameter of the opening in the die set located at the radial extension of the die surface. As the cylindrical band is forced into the annular space between the concave and convex die surfaces, the band gradually curls inward under compression to meet the semi-annular space. Thus, the cylinder is placed under compressive force and the annular outer surface of the workpiece conforms exactly to the die concavity.

In a preferred method of forming annular shells suitable for couplings or converters such as automotive torque converters, the free ends of the bands are preferably welded. The weld is wiped and compressed into the annular, concave surface of the die as the band is gradually curled inward, bringing the welded surface into exact alignment with the die concavity.

Thus, the weldment does not undergo tensile failure as in the prior art methods described above. As understood, the weld is not pure like the base metal, but approximately
Destructive for commercial use when expanded by 20%. There is no known limit to compressive force. Furthermore, since the semi-annular shell can be formed by the method of the present invention in one press stroke, there is no need to pre-form the flared end of the cylinder (of course, the semi-annular shell can be pressed again in a re-strike die). (can be made into more complex shapes). Finally, the non-critical surface of the annular shell is easily kept within precise tolerances as it precisely coincides with the die concavity under compressive curling forces.

Other advantages and features of the invention will be more fully understood from the following detailed description of the method of the invention.

FIG. 1 shows a thin-walled, annular channel or semi-annular shell 20 formed by the method of the present invention. Shell 20 consists of a cylindrical outer lip 22, a U-shaped intermediate section 24, and an inner lip 26. Ciel 20
is formed from a cylindrical band 30 as shown in FIG. The cylindrical band 30 is formed from a rolled flat straight strip and welded at 28 to form a weld to the semi-annular shell shown in FIG.
The formation of a cylindrical band 30 as shown in FIG.
Further details are provided in issue 3851517.

The semi-annular shell 20 of FIG. 1 is formed by a die set assembly 34 shown in FIGS. 3 and 4. Die set assembly 34 includes an annular cylindrical ram 36 that enters a cylindrical bore 40 in riser 38. Riser 38 includes a conical counterbore 42 that receives cylindrical band 30 when ram 36 is raised above the position shown in FIG. Ram 36 includes an annular lip 44 and an end 46 that engage cylindrical band 30.

The cylindrical band 30 first enters a curling die 50 having an annular cylindrical surface 52 receiving the cylindrical band and an annular concave surface 54 terminating in a cylindrical hole 56 . The annular forming post 60 that enters the curl die 50 is
It has an outer cylindrical surface 62 opposite the cylindrical surface 52 of the curling die, and an annular convex surface 64 opposite the concave surface 54 of the curling die. The forming post 60 and curling die 50 thus form a U-shaped annular space that receives the cylindrical band 30 as described below.

Die set assembly 34 also includes a static, cylindrical center post 66, a spring pad 68, and a plurality of coil springs 70 biased against cylindrical insert 58 within molded post 60. A central guide post 72 having a cylindrical outer surface receives the ram 36 in telescopic relationship, and the ram includes a conical flange 74 that receives a die pin 76. Die pins 76 are bolted or otherwise secured to an upper die platen (not shown). In the disclosed embodiment, there are four die pins 76 and four coil-o-springs 70. Only one half of the die assembly is shown to illustrate the method of the present invention, and the die assembly typically includes a lower die platen (not shown) supporting the curl die 50 of a conventional bolster assembly.
It will be understood by those skilled in the art to include. Reference is also made to the aforementioned US patents.

The method of the present invention includes the steps of forming the cylindrical band 30 of FIG. 2 from a flat strip stock and welding the free ends of the strips, indicated at 28. As previously mentioned, the free ends of the bands may also be joined by other means, including Teig welding. In fact, the method of the invention compresses the band during forming, so that the band is formed into a U-shaped annular channel without joining its abutting free ends.

Next, one end of the cylindrical band 30 is attached to a curl die 5.
0 and into the semi-annular space defined by the molded post 60. The opening to the semi-annular space in the preferred embodiment is provided by opposing cylindrical surfaces 52, 62.
It is cylindrical as defined by . As shown, the cylindrical opening fits smoothly into the semi-annular space defined by the annular concave surface 54 and the annular convex surface 64. The nominal diameter of the cylindrical band 30 is equal to the nominal diameter of the cylindrical opening between the curling die 50 and the forming post 60. Opposite ends of the cylindrical band are engaged by the annular lip 44 of the ram 36. Thus,
The lowering of the ram 36 pushes the cylindrical band downward in FIG.
Gradually curl the band radially inward between the
The cylindrical band and weld 28 are compressed as shown in FIG. Thus, the semi-annular shell 20 is formed in one pass of the press, eliminating the need for a preforming step as described in the cited patents.

As previously stated, the method of the present invention provides a 50% material cost savings over current methods that involve die forming a semi-annular shell from a washer shaped blank. The outer surface of the semi-annular shell closely matches the concave surface 54 of the curling die as it curls inward and compresses the band to conform the band to the curling die. More importantly, the weld 28
Since the weld is placed under compression, tensile failure of the weld as experienced in the method described in the cited patent is eliminated. Additionally, the outer surface of the weld 28 is wiped with a concave surface 54 so that the weld closely matches the concave surface 54. Because the band is placed under compression rather than tension during molding, the band does not tend to pull away from the die outer surface, maintaining the outer critical surface within tolerances.

The semi-annular shell 20 is formed in more steps depending on the application. For example, a coring impeller for an automobile fluid converter is 80 in FIG.
It includes a cylindrical inner surface that receives the shaft as shown in .
This shape is formed using a restriking die set as shown in FIG. Semi-annular shell 80 shown in FIG.
includes a cylindrical inner lip portion 82 and an outer semi-annular portion 84.

The restriking die assembly includes a female die member 86 corresponding to the curling die 50 of FIGS. 3 and 4 and an annular concave surface 8 that receives a static, cylindrical center post 92.
It has 8. Shaped post 94 includes an annular convex surface 96 and a cylindrical surface 98. As previously discussed with respect to FIGS. 3 and 4, female die member 86 and molded post 94 are spaced apart to define a semi-annular space therebetween, and semi-annular shell 8
0 is formed by a die member.

In the disclosed embodiment of the restriking die assembly shown in FIG.
02 and an inner retainer ring 104 which sees an annular lip 106. Semi-annular shell 2 shown in Figure 1
0 is inserted into the female die member 86 and the forming post 94 and retainer rings 100, 104 are lowered into the female die to form the final shape of the semi-annular shell 80 shown in FIG. Changes in the shape of the shell can be better understood by comparing FIGS. 7 and 8. FIG. 7 shows the cross-sectional shape of the semi-annular shell 20 of FIG. 1, and FIG. A cross-sectional shape of a semi-annular shell 80 is shown. The restriking die assembly unfolds the shell and reshapes the cylindrical outer lip into a continuous, outer half-annular portion 84 as shown in FIG.
The inner lip 26 is then reshaped into a cylindrical lip 82 as shown in FIG.

EFFECTS OF THE INVENTION The method of the present invention thus significantly reduces the cost of forming a semi-annular shell by rolling and welding a rectangular strip of sheet material as shown in FIG. 2 to form a shell. This results in substantial savings in material. Additionally, the shell is formed in one press stroke, as shown in FIGS. 3 and 4, without applying tensile stress to the weld 28. The shell can be molded from various materials depending on the application. For example, a coring impeller may have a thickness of e.g. 101 cm (0.040 in).
Can be formed from 0 or 1018 steel plate. As previously mentioned, the weld 28 is placed under compression during the curling process as shown in FIGS. 3 and 4. The outer lip 22 of the shell is widened in the restriking die set assembly shown in FIG.
Its expansion is less than 10% to avoid destruction of the weld. Thus, the method of the present invention can form semi-annular shells 80 of complex shapes, as shown in FIG. 5, while avoiding tensile forces on the weld that would otherwise break the weld during manufacture.

[Brief explanation of the drawing]

FIG. 1 is a side view of a semi-annular shell formed by the method of the present invention. 2 is a side view of the cylindrical band forming the semi-annular shell of FIG. 1; FIG. FIG. 3 is a side, partial cross-sectional view of one embodiment of a die set used in the method of the invention,
Figure 2 shows the ram starting condition for forming the cylindrical band of Figure 2; 4 is a side cross-sectional view of the die set shown in FIG. 3, with the ram lowered to form the semi-annular shell shown in FIG. 1; FIG. Figure 5 shows
Figure 2 shows the semi-annular shell of Figure 1 after restriking.
FIG. 6 is a side cross-sectional view of a portion of an embodiment of the restriking die used to form the semi-annular shell of FIG. 5. FIG. 7 is a side cross-sectional view of the semi-annular shell shown in FIG. 1. FIG. 8 is a side cross-sectional view of the semi-annular shell shown in FIG. 5. FIG. Explanation of symbols in the drawings: 20, 80...Semi-annular shell, 28...Strip free end (or welded part), 30...Cylindrical band, 34...Die set assembly, 36...Ram, 38...Riser , 50... Curl die, 58... Insert, 60... Molded post, 66... Center post,
70...Coil spring, 72...Center guide post, 74...Conical flange, 76...Die pin.

Claims (1)

[Claims] 1 (a) A rectangular flat sheet having a free end and upper and lower edges is formed into a cylindrical band, the free ends are brought into contact with each other, and the upper and lower edges are used to connect the upper and lower ends of the cylindrical band. (b) joining the mating ends; (c) joining one end of the cylindrical band to the radially outer side of the semi-annular space with concave and convex fixing die surfaces that align at approximately equal intervals; The cylindrical band between the fixed die surfaces is pushed into the semi-annular space defined between the die members having an opening with the same diameter as the nominal diameter of the cylindrical band at a portion thereof and engaged with the other end of the cylindrical band. The cylindrical band is shaped into a semi-annular shape by gradually curling the cylindrical band radially inwardly between the concave and convex die surfaces in the semi-annular space and compressing the joint between the cylindrical band and the mating end. U consisting of a process of shaping into a shape, characterized in that the workpiece is shaped in one pass and is under compression during the entire shaping process
A method for forming thin-walled, semi-annular shells with a letter-shaped cross section. 2 (a) A step of forming a rectangular flat sheet having a free end and upper and lower edges into a cylindrical band in which the free ends are brought together; (b) A step of welding the joining ends of the cylindrical band; ( c) having a cylindrical opening on the outside in the radial direction, and forming a semi-annular space that smoothly blends from the cylindrical space to the semi-annular space adjacent to the opening, with substantially equally spaced opposing concave and convex surfaces; providing a single die set having a fixed die surface; and (d) forcing one end of the cylindrical band into the cylindrical opening by engaging the other end of the band and placing the band under compression. an annular outer surface that is progressively curled into a semi-annular space between the concave and convex fixed die surfaces, wiping and compressing the weld to the concave die surface, and causing the cylindrical band to precisely mate with the concave die surface; forming a thin-walled, semi-annular shell with a U-shaped cross section, characterized in that the workpiece is formed in one pass and is under compression during the entire forming process. Law. 3 (a) Forming a rectangular flat sheet having free ends into a cylindrical band by butting the free ends; (b) Joining the butting ends of the cylindrical band; (c) ) one end of said cylindrical band having at its radially outer side a cylindrical opening and substantially equidistantly aligned concave and convex fixed die surfaces forming an opening of a U-shaped space that blends smoothly with said cylindrical opening; inserting into a single die set; and (d) forcing the cylindrical band between the concave and convex die surfaces by engaging the other end of the band, curling the cylindrical band inwardly; The step of precisely matching the outer surface of the cylindrical band with the outer concave surface of the die and compressing the joint between the mating ends of the band to form a channel-like shell of approximately U-shaped cross section; A process for forming thin-walled, channel-shaped, almost U-shaped cross-sections, characterized in that they are formed in one pass and are under compression during the entire forming process. 4 (a) bending a rectangular flat sheet having free ends into a cylindrical band by abutting the free ends; (b) joining the abutting free ends of the cylindrical band; (c) ) having a cylindrical outer opening having the same diameter as the cylindrical band, defining a cylindrical space in the outer opening that blends smoothly with the inwardly curved concave and convex surfaces, and defining a U-shaped space communicating with the cylindrical space; inserting one cylindrical end of said cylindrical band into a single die set having regularly spaced die members; (d) forcing said cylindrical band into said die set space and gradually curling said cylindrical band under compressive force; forming a semi-annular shell having a cylindrical outer lip and a U-shaped intermediate portion terminating in a circular inner lip; and (e) re-striking said semi-annular shell between opposing die members to form said outer lip; Expand by 10% or less within the allowable stress of the joint between the abutting ends,
a continuous, U-shaped half with a cylindrical inner lip, characterized in that the workpiece is formed in one stroke and under compression during the entire forming process; Method for forming thin-walled, semi-annular shells of U-shaped cross section with an annular outer part.